Turkey Vulture has a tiny, unfeathered head, holds its wings in a dihedral and has contrastingly paler flight feathers while Black Vulture has white outer primaries and quite different, snappy wingbeats. Immature Bald Eagles are similar (very large and dark overall) but differ in fundemental aspects of shape. Golden Eagles are smaller-headed, smaller-billed and somewhat slimmer-winged than Bald Eagles and fly with wings held in a dihedral. Immature Bald Eagles always have patchy white underwings and (occasionally) bellies. Golden Eagles have crisp white patches restricted to the inner primaries and base of tail. Immature Golden Eagles have yellow ceres while immature Balds have dark ceres, a useful mark for perched birds. At great heights, dark morph buteos can be similar but are always shorter-winged with more diffuse white areas on underwings and different tail patterns.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.